In recent years, reduction in size of IC chips has proceeded. In such small-sized IC chips, an IC chip with an antenna mounted thereon is known (see Patent Literature 1, for example). The possibility of applying such a small-sized IC chip to various industries has been widely studied. A specific example for which study was made includes an application to a small-sized concave portion made of a metal having a narrow space (assembling which includes embedding or mounting). In this case, a small-sized IC chip (having a size of, for example, 0.5 millimeters×0.5 millimeters or smaller) is provided on a bottom part of a concave portion of a small-sized metal body and is configured to enable wireless communication (transmission and receiving of radio waves for writing and reading of information) between itself and a reader/writer.
Here, it is assumed that a good antenna efficiency is realized in the case where an antenna on the reader/writer side has a size substantially equal to the opening area of the antenna on the small-sized IC chip side. Unless the antenna on the reader/writer side is located in abutting contact with or in proximity to a small-sized IC chip within a small-sized concave portion, it is difficult to appropriately perform wireless communication between the antenna on the reader/writer side and the small-sized IC chip due to the influence of reflection or the like by a concaved wall surface, which may cause a trouble in information writing/reading. Thus, there is a demand for such a small-sized antenna as to match to an antenna on the small-sized IC chip side.
On the other hand, there is known a small-sized antenna of this type which includes a ground plate having a flat plate shape, a first core member provided on the ground plate and formed using a soft magnetic material having a columnar shape, and a wire wound in a spiral shape around the first core member (see Patent Literature 2, for example).